Various structures for use in growing plants are known, including as described in the following US patent documents: U.S. Pat. No. 7,921,599, Irwin, Vegetation support system, 12 Apr. 2011; U.S. Pat. No. 5,826,375, Black, Modular planter studio, 27 Oct. 1998; U.S. Pat. No. 5,042,196, Lukawski, Apparatus for cultivation, 27 Aug. 1991; U.S. Pat. No. 3,757,470, Shimamato, Apparatus for cultivation, 11 Sep. 1973; U.S. Pat. No. 6,502,350, Dick, Apparatus for cultivation, 7 Jan. 2003; U.S. Pat. No. 7,877,927, Roy, Modular hydroponic, 1 Feb. 2011; U.S. Pat. No. 7,832,144, Corradi, Hydroponic growing system, 16 Nov. 2010; U.S. Pat. No. 7,243,460, Darlington, Support for vertical plant matrix, 17 Jul. 2007; U.S. Pat. No. 8,689,485, Friedman, Vertical planter and gardening wall, 8 Apr. 2014; U.S. Pat. No. 8,365,466, Storey, Hydroponic display, 5 Feb. 2013; U.S. Pat. No. 7,926,224, Sotiri, Green planting wall, 19 Apr. 2011; U.S. Pat. No. 6,725,601, Chick, Vertical ecosystem, 27 Apr. 2004; U.S. Pat. No. 7,080,482, Bradley, Modular plant growing, 25 Jul. 2006; U.S. Pat. No. 6,634,138, Katzman, Self sustaining indoor waterfall, 31 Oct. 2003; U.S. Pat. No. 6,178,692, Graven, Lighting system for vertical garden, 30 Jan. 2001; U.S. Pat. No. 8,418,403, Nuttman, Hanging stacked plant holders, 16 Apr. 2013; and U.S. Pat. No. 7,627,983, Deutsch-Aboutmahassine, Modular wall mounted growing system, 8 Dec. 2009.
The Black patent (U.S. Pat. No. 5,826,375) discloses a modular planting system comprising a plurality of horizontally extending troughs suitable for supporting plant containers, each trough positioned one above the other, with a vertical drainage conduit connecting each pair of adjacent troughs. Each drainage conduit is affixed to the upper of the pair of adjacent troughs (e.g., “Conduit 32 may be integrally formed with trough 28 or it may individually constructed and lockingly inserted into trough 28 such as by means of glue or the like.” Black, col. 4, lines 60-63). The upper end of each drainage conduit projects above the inner bottom of the relevant trough so as to define a maximum water depth in the trough, in that, water above the upper end of the drainage conduit flows down the drainage conduit.